 
 (defn- normalized-values
   [examples field]
-  (let [values (get-values examples field)
-        flattened (cond-> values
-                    (coll? (first values)) flatten-list-values)]
-    (map #(cond-> % (string? %) string/lower-case)
-         flattened)))
+  (let [values (get-values examples field)]
+    (cond-> values
+      (coll? (first values)) flatten-list-values)))
 
 (defn- check-from-to
   [from-str to-str]

            1)
        "[from to[ should not exceed one year")))

(defn- test-cardinality
  "test one field cardinality, examples are already created."
  [examples entity field]
  (testing (format "cardinality %s %s" entity field)
    (let [expected (-> (normalized-values examples field)
                       set
                       count)
          _ (assert (pos? expected))
          {{:keys [from to]} :filters
           :as res} (cardinality entity

                                  :from "2020-01-01"}
                                 {:aggregate-on (name field)})]
      (is (= expected
             (get-in (:data res) (parse-field field)))
          (error-helper-msg unique-values))
      (check-from-to from to))))

(defn- test-topn
  "test one field topn, examples are already created."
  [examples entity field limit]
  (testing (format "topn %s %s" entity field)
    (let [prepared (->> (normalized-values examples field)
                        frequencies
                        (sort-by val)
                        reverse)
          expected (vals (take limit prepared))
          _ (assert (every? pos? expected))
          {{:keys [from to]} :filters
           :as res} (topn entity
